1. Field of the Invention
The present invention relates to a technique for white balance adjustment in a digital camera.
2. Description of the Related Art
In a digital camera such as a digital still camera or a video camera, the reproduced color for a given subject vary depending on differences in the spectrum of the light source. For this reason, white balance adjustment is performed so that the color of a white subject in a shot image may be reproduced as white. White balance adjustment typically involves adjusting gains of the red and blue image signals or of the image data on the basis of color component in the shot image. In such gain adjustment, respective cumulative values (integration values) of the red component, the blue component, and the green component of white pixels constituting the shot image are calculated, and setting of gains is carried out on the basis of the integration values so calculated. These integration values are dependent on gains and on the number of white pixels in the image as well. Accordingly, in order to carry out white balance adjustment in a manner irrespective of conditions of the shot image such as the number of white pixels, white balance adjustment is performed through repeated fine adjustment of gains based on color component in the gain-adjusted image.
However, completion of white balance adjustment (also termed “white balance convergence”) is determined by comparing integration values of several color components (e.g. the red component and the green component) and detecting reversal of magnitude relationship of these integration values. For this reason, since color component integration values observed subsequent to fine gain adjustment are used for the determination of white balance convergence, there is a risk that, depending on conditions of the light source or the subject during shooting, determination of white balance convergence fails in some instances.